It is well known that information arrival has an impact on prices volatility, and trading volume in financial markets (see e.g., Goodhart and O'Hara 1997). Scheduled macroeconomic announcements, such as monthly employment figures, consumer prices, or building permits, stand out from the steady...

Reliable estimates of variances and covariances are crucial for portfolio management and risk controlling. This paper investigates alternative methods to estimate time varying variance-covariance matrices: ordinary estimates and exponentially weighted moving averages in comparison to Markov...